Friends of the family say Pauline Hickey, who had been living in the English capital for several years, is heartbroken after she discovered the scene of the horrific crime just 100 yards from her home and tried to comfort the dying boy, Hani Abou El Kheir.

"We are trying to calm her down. She was up all night crying and is exhausted,” said friend Mahmoud Abosiad.

"He was a lovely boy. He did not deserve to end up on a slab."

Hani was set upon on the edge of Pimlico, one of London's most affluent neighbourhoods, at 7pm on Sunday in a suspected drugs-related attack.

Emergency services battled to save the teenager's life as he lay bleeding in Lupus Street, but he died a few hours later in hospital.

Scotland Yard said police were "retaining an open mind regarding any motive at this stage" and confirmed a post-mortem examination into his death will take place at noon today. No arrests have been made.

Last night it emerged Hani had become known to drugs intervention workers, and was believed to be "on the periphery" of local gangs.

David Savizon, who works for the Westminster Council's Your Choice anti-gangs programme, said Hani's name had been flagged up to drugs workers last week, and he was due to get a visit from outreach workers if it came up again.

Mr Savizon, 34, said: "Unfortunately I wasn't able to meet him. He wasn't deemed significant in terms of being in a gang. He was mentioned as someone on the periphery."

Mr Savizon, who has 12 years of experience working with youngsters at risk of joining gangs, added: "It was more of a bookmark just to see where this young person was.

"Everything I have heard about him...he was a very timid young man."

Mr Savizon said that even if the murder victim was not a senior drugs figure he could still be at risk of being targeted. "It is a very dangerous activity," he said.

The attack happened near Pimlico Underground station, and Lupus Street is bordered by extensive council estates on one side and is home to Pimlico Academy.

The Churchill Gardens estate where Hani lived has become a drugs blackspot in the last year.

Children as young 10 are paid "tens of pounds" to stash drugs and ferry them around. There is not an established network of drugs gangs.

"The Churchill Gardens estate has become a bit of a hotspot in the last 12 months for drugs," said Mr Savizon.

"We are really trying to identify who we need to be working with and the community needs to take some accountability for it, they know a lot of what is going on."

He added: "We are really concerned about the impact of drugs and the competition between dealers and young people being recruited."

Mr Savizon said Pimlico was seen as "an opportunity" by drug dealers.

A 58-year-old resident, who did not want to be named, said there had been two murders in nearby Gloucester Street in recent years and a stabbing of a boy outside a row of shops in Lupus Street before Christmas.

"The violence that has started to occur around here is something else, it is frightening for all the residents," she said.

Mohammed Alzubaidi, 49, from nearby Peabody Close, said his friend witnessed a gang of black and white teenagers carrying out the attack.

"He said they were carrying knives, some of them with wide swords. He said the victim was screaming and trying to get away."

He said: "My flatmate saw him bleeding out. He said he could see the wound bleeding out from all the way up here. He saw three or four guys running off up the street."

Jerry Collins, Hani's former principal said: "The pupils and staff at Pimlico Academy were deeply saddened to hear about the death of our former student Hani Abou El Kheir and extend our deepest sympathies to his family."

Hani was popular and conducted himself in an "exemplary manner", Mr Collins added.

Detectives continued to appeal for witnesses to the attack, which they believe was carried out by "several youths".